Method and apparatus for spraying liquid material

ABSTRACT

Liquid material to be sprayed is fed to a spray gun by feeding solid material into an endless conveying path, circulating the material around the path while the material is being heated to a predetermined temperature, discharging some of the heated material to the spray gun, and feeding further solid material into the conveying path. Apparatus suitable for spraying marking material onto road or other surfaces is described for carrying out the above method.

United States Patent [191 [111 3,910,323 Harding et a1. Oct. 7, 1975 [54] METHOD AND APPARATUS FOR 3,359,970 12/1967 Pedersen et a1. 222/146 H SPRAYING LIQUID MATERIAL [75] Inventors: John Harding; Peter Placz'ek, both Primary Examiner Houston Be",

of crawley England Attorney, Agent, or Firm-Neil F. Markva [73] Assignee: Prismo Universal Limited, Crawley,

England [22] Filed: Apr. 5, 1974 [57] ABSTRACT 21 A l N 458 268 1 pp 0 Liquid material to be sprayed is fed to a spray gun by feeding solid material into an endless conveying path, 14 circulating the material around the path while the ma- 2/ 146 H terial is being heated to a predetermined temperature, [51] Int. Cl? B65B 3/04 di harging some of the heated material to the spray Field of Seal'dl 222/146 gun, and feeding further solid material into the conl1 veying path. Apparatus suitable for spraying marking material onto road or other surfaces is described for References Cited carrying out the above method.

UNITED STATES PATENTS 3,305,138 2/1967 Plumb 222/146 H 18 Claims, 1 Drawing Figure SWITCH COLD MATERIAL SUPPLY SPRAV GUN METHOD AND APPARATUS FOR SPRAYING LIQUID MATERIAL BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method and apparatus for spraying liquid material. More particularly but not exclusively, the invention relates to a spraying of a marking material onto road or other surfaces.

2. Prior Art When marking road surfaces with white or yellow lines it is usual to take a required quantity of the marking material in block form, heat the block in a container until it has liquefied and been raised to the required spraying temperature, e.g. 400F., and then discharge the hot liquid material from the container to a spray gun which is used for applying the material to the road surface. This process is a batch process and requires the estimation of how much material is required at any one time.

SUMMARY According to the invention there is provided a method of feeding liquid material to be sprayed to at least one spray gun, comprising feeding solid material into an endless conveying path, circulating or allowing the material to circulate around said path, heating the material as it circulates until at least a part of the material is liquefied and raised to a predetermined temperature, discharging at least a portion of said part of the material from the conveying path as a feed for one or more spray guns, and feeding further solid material into the conveying path.

The hot liquid material may be continuously discharged from the conveying path, further solid material being constantly fed into the conveying path. For example, this occurs during the spraying of a continuous edge line onto a road surface. Alternatively the hot liquid material may be intermittently discharged from the conveying path when, for example, it is desired to apply dash lines in the center of the road surface. In this case the further solid material is also fed intermittently into the conveying path in timed relation and in a proportionate quantity to the liquid material discharged. However, the essence of all operations in accordance with this invention is that there is provided a process which is capable of continuously feeding hot liquid material to the spray gun or guns, the material being heated from its initial solid form into a state ready for application, as and when it is required. a I

The invention also provides apparatus for feeding liquid material to be sprayed to at least one spray gun, comprising an enclosure around which the material circulates or is circulated, means for feeding solid mate- 'rial into the enclosure, means for heating the material while in the enclosure to liquefy at least a part of the material and to raise that part to a predetermined temperature, and an outlet for discharging at least a portion of said part of the material from the enclosure as a feed for one or more spray guns.

The apparatus includes at least one spray gun and a feed pipe connecting the spray gun to the discharge outlet of the enclosure. In this case, means for actuating the spray gun are preferably linked to the means for feeding solid material into the enclosure whereby intermittent use of the spray gun results in a proportional intermittent feed of solid material into the enclosure.

Also, means are provided for recirculating liquid material discharged from the enclosure but not from the spray gun.

Preferably the enclosure has a screw conveyor for circulating the material therethrough.

The enclosure may be provided with at least one heating jacket e. g. filled with heated oil, for heating the material in the enclosure the path having a generally constant cross-sectional area. In a case in which it is desirable to heat the material progressively to two, three or even more different temperatures depending on the location of the material along the conveying path, a plurality of heating jackets are provided, one jacket for each temperature step. Preferably the heating jacket provided for heating the material to the highest temperature is disposed adjacent the enclosure outlet.

Preferably the solid material fed into the enclosure is a thermoplastics resinous material suitable for marking road surfaces. The material is preferably fed into the enclosure in powder form.

BRIEF DESCRIPTION OF THE DRAWING The drawing shows, by way of example, a diagrammatic layout, in plan view, of apparatus for spraying marking material onto a road surface.

DESCRIPTION OF THE PREFERRED EMBODIMENT This example relates to the application of a thermoplastics resinous material to road surfaces, e.g. for the application of yellow and white lines thereon. Such material has to be heated in this embodiment from cold, to a temperature of about 400F. and is then sprayed onto the road surface. Referring to the drawing, there is shown a layout of an apparatus for providing a continuous feed of marking material at the required temperature for use as and when required. The apparatus comprises an enclosure 10 housing a plurality of screw conveyors 11 mounted horizontally side by side and driven through a gear train by an electric motor 12 for circulating the material through the enclosure along a continuous zig-zag path defined by baffles within the enclosure. The material is returned from the downstream end of the last conveyor 11 to the upstream end of the first conveyor 11 by a short conveyor 41 driven by intermeshing gears on the last conveyor 11 and the conveyor 41. A further screw conveyor 14 driven by another electric motor 15 and leading from a hopper 16 feeds the cold material into the enclosure, the material being in a solid, powdered form. The material is then heated within the enclosure by two oil jackets, one jacket 17 surrounding that part of the enclosure located adjacent the feed point for the enclosure and the other jacket 18 surrounding the remainder of the enclosure located adjacent a discharge outlet 19 from the enclosure. Two burners 20, 21 supplied with fuel from a tank 22 are provided to heat the oil in the jackets l7, 18. The burner 21 is capable of raising the temperature to about 400F., i.e. the temperature at which it is desired to apply the material to the road surface, and the burner 20 is in fact a less powerful burner since it has been found that with this particular material, if the material is heated to too high a temperature too quickly, then the material tends to discolor and also to stick to the blades of the screw conveyors. For this reason, it it important that the more powerful burner 21 is located at or adjacent the downstream section of the conveyor path, i.e. adjacent the discharge outlet 19.

The two oil jackets 17, 18 are interconnected by a common expansion tank 23. Separate pumps 30, 31 are provided for circulating the oil through the jackets l7, 18 respectively.

If desired three or more heating jackets may be provided for heating the material progressively up to 400F in stages other than two. Each heating jacket would be provided with its separate burner. In a further embodiment, only one heating jacket is provided for heating the material.

A conduit 24 leads from the discharge outlet 19 of the enclosure to a mixer 25 which gives a final mix to the material and then to a pump 26 which pumps the material to a pair of spray guns 27. Only one, or more than two spray guns may be provided if desired. A further conduit 28 is provided to recirculate material from the spray guns 27 to the enclosure 10 to maintain the material continuously in circulation even when no spraying is taking place. The pump 26 is provided with a surge tank 29 to provide an even flow of material to the spray guns. The conduits 24, 28, the mixer 25, the pump 26 and surge tank 29 and the spray guns 27 are all jacketed by the above-mentioned oil jacket 18 for the hotter part of the enclosure 10.

A floatation device 32 is provided adjacent the discharge outlet 19 of the enclosure 10 to maintain a substantially constant level of material in the enclosure, the device being connected to an electrical switch 33 for switching on and off the motor for the feed screw 14. Flotation device 14 also includes an override switch.

In operation, the hopper is filled with the thermoplastics resinous material in a cold powdered form. The feed screw 14 is actuated to allow the material to pass into the enclosure 10 around which it is circulated by the screw conveyors 11. Fuel is pumped to both burners 20, 21 where it ignites and heats the oil in the jackets 17, 18. The temperature of the oil within the jackets 17, 18 and the operation of the burners 20, 21 is thermostatically controlled. The solid material fed into the enclosure 10 is thereby liquefied and heated to form a mass of material at the discharge outlet 19 which is at the required temperature of 400F., the material being continuously circulated around the enclosure by the screw conveyors 11. At any time the feed of further solid material to the enclosure 10 may be stopped by switching off the feed screw 14.

When the material has been heated to the required temperature, the material may be sprayed onto a road surface by the spray guns 27. To achieve this, the pump 26 is operated to discharge the hot liquid material from the enclosure through the mixer and along the conduit 24 to the spray guns 27 which are then actuated for the desired time. With the pump 26 operating and the spray guns 27 switched off, the material will be recirculated to the enclosure by conduit 28. The same will apply to any excess material during operation of the spray guns 27.

During spraying, the material discharged from the system will be automatically replaced by the motor 15 operating the further screw conveyor 14 to feed an equivalent quantity of cold, solid material into the heated material circulating around the enclosure 10, this process of topping up the enclosure being controlled by the flotation device 32 causing the motor 15 to be switched on or off as required to maintain a substantially constant level of material in the enclosure. There is thus provided a continuous process of supplying the spray guns 27 with marking material heated to the required temperature, the material being circulated around the enclosure 10 so that it may be used as and when required. In other words, all of the material is circulated continuously at substantially the same rate of feed.

The invention is not limited to materials for marking road surfaces but may be applied to the heating and subsequent discharge of other materials for application to surfaces. Also, the cold material need not be in powdered form provided that it is in a form readily feedable into the enclosure 10, e.g. the material may be granulated.

Furthermore, the screw conveyors 11, 14 may be replaced by other conveying means. For example, the material may be vibrated or blown along the conveying path, or alternatively the circulation may be achieved partly be gravity.

It is envisaged that the apparatus of the above embodiment would be used for applying yellow or white lines. However, it may be desired to apply simultaneously yellow and white lines. In this embodiment, two complete spraying units are coupled together, one for the discharge of yellow marking material and the other for discharge of white material. The controls of the two units would be connected to ensure that the spraying operations of the two units coincided.

We claim:

1. A method of feeding liquid material to be sprayed to at least one spray gun, comprising:

a. feeding solid material into an endless conveying path,

b. circulating or allowing the material to circulate around said path,

c. heating the material as it circulates until at least a part of the material is liquefied and raised to a predetermined temperature,

(1. discharging at least a portion of said part of the hot liquefied material from the conveying path as a feed for at least one spray gun, and

e. feeding an equivalent amount of further solid ma terial into the conveying path.

2. A method as claimed in claim 1, wherein the hot liquid material is continuously discharged from the conveying path, further solid material being constantly fed into the conveying path.

3. A method as claimed in claim 1, wherein the hot liquid material is intermittently discharged from the conveying path, the further solid material being fed intermittently into the conveying path in timed relation and in a proportionate quantity to the liquid material discharged.

4. Apparatus for feeding liquid material to be sprayed to at least one spray gun, comprising:

a. an enclosure defining a continuous conveying path,

b. means for feeding solid material into the enclosure, the material circulating or being circulated around the conveying path,

c. means for heating the material while the material is circulating around the conveying path in the enclosure to liquefy at least a part of the material and to raise that part to a predetermined temperature, and

d. an outlet from the enclosure for discharging at least a portion of said part of the material from the conveying path as a feed for at least one spray gun.

5. Apparatus as claimed in claim 4, including at least one spray gun and a feed pipe connecting the spray gun to the discharge outlet of the enclosure.

6. Apparatus as claimed in claim 5, wherein the feeding means includes means for controlling the amount of solid material fed into the enclosure to maintain a substantially constant level of material in the enclosure whereby intermittent use of the spray gun results in a proportional intermittent feed of solid material into the enclosure.

7. Apparatus as claimed in claim 5, including means for recirculating liquid material directly back to the enclosure when not discharged from the spray gun.

8. Apparatus as claimed in claim 4, wherein the enclosure has a screw conveyor for circulating the material therethrough.

9. Apparatus as claimed in claim 4, wherein the enclosure is provided with at least one heating jacket for heating the material in the enclosure.

10. Apparatus as claimed in claim 9 for heating the material progressively to two or more different temperatures depending on the location of the material along the conveying path, including a plurality of heating jackets, one jacket for each temperature step.

11. Apparatus as claimed in claim 10, wherein the heating jacket provided for heating the material to the highest temperature is disposed adjacent the enclosure outlet.

12. Apparatus as claimed in claim 4, wherein the solid material fed into the enclosure is a thermoplastics resinous material suitable for marking road surfaces.

13. Apparatus as claimed in claim 4, wherein the material is fed the the enclosure in powder form.

14. Apparatus as claimed in claim 4, wherein the conveying path is a zig-zag path defined by baffles in the enclosure, the path having a generally constant cross-sectional area.

15. Apparatus for spraying material, comprising:

a. an endless, closed-loop, elongated enclosure defining a continuous conveying path,

b. means for feeding solid material into said enclosure,

c. means for conveying said material through the entire enclosure, along said conveying path,

d. means for heating said material to a predetermined temperature while it is being conveyed to produce a liquefied pan of the material, and

e. outlet means for discharging at least a portion of said liquefied part from the enclosure,

f. said outlet means including'at least one spray gun and means for recirculating liquefied material which has not been discharged from the spray gun directly back into said enclosure,

g. said apparatus being adapted to be transportable on a vehicle.

16. Apparatus as claimed in claim 15, wherein the enclosure includes at least one heating jacket disposed around the enclosure for heating the material being conveyed within said enclosure.

17. An apparatus as claimed in claim 16, wherein there is a plurality of heating jackets disposed around different portions of said conveying half, and there is a means for heating each of the heating jackets at a different temperature with respect to each other.

18. Apparatus as claimed in claim 15, wherein said feeding means includes means for controlling the amount of solid material fed into the enclosure in response to an amount of liquefied material being discharged from said enclosure. 

1. A method of feeding liquid material to be sprayed to at least one spray gun, comprising: a. feeding solid material into an endless conveying path, b. circulating or allowing the material to circulate around said path, c. heating the material as it circulates until at least a part of the material is liquefied and raised to a predetermined temperature, d. discharging at least a portion of said part of the hot liquefied material from the conveying path as a feed for at least one spray gun, and e. feeding an equivalent amount of further solid material into the conveying path.
 2. A method as claimed in claim 1, wherein the hot liquid material is continuously discharged from the conveying path, further solid material being constantly fed into the conveying path.
 3. A method as claimed in claim 1, wherein the hot liquid material is intermittently discharged from the conveying path, the further solid material being fed intermittently into the conveying path in timed relation and in a proportionate quantity to the liquid material discharged.
 4. Apparatus for feeding liquid material to be sprayed to at least one spray gun, comprising: a. an enclosure defining a continuous conveying path, b. means for feeding solid material into the enclosure, the material circulating or being circulated around the conveying path, c. means for heating the material while the material is circulating around the conveying path in the enclosure to liquefy at least a part of the material and to raise that part to a predetermined temperature, and d. an outlet from the enclosure for discharging at least a portion of said part of the material from the conveying path as a feed for at least one spray gun.
 5. Apparatus as claimed in claim 4, including at least one spray gun and a feed pipe connecting the spray gun to the discharge outlet of the enclosure.
 6. Apparatus as claimed in claim 5, wherein the feeding means includes means for controlling the amount of solid material fed into the enclosure to maintain a substantially constant level of material in the enclosure whereby intermittent use of the spray gun results in a proportional intermittent feed of solid material into the enclosure.
 7. Apparatus as claimed in claim 5, including means for recirculating liquid material directly back to the enclosure when not discharged from the spray gun.
 8. Apparatus as claimed in claim 4, wherein the enclosure has a screw conveyor for circulating the material therethrough.
 9. Apparatus as claimed in claim 4, wherein the enclosure is provided with at least one heating jacket for heating the material in the enclosure.
 10. Apparatus as claimed in claim 9 for heating the material progressively to two or more different temperatures depending on the location of the material along the conveying path, including a plurality of heating jackets, one jacket for each temperature step.
 11. Apparatus as claimed in claim 10, wherein the heating jacket provided for heating the material to the highest temperature is disposed adjacent the enclosure outlet.
 12. Apparatus as claimed in claim 4, wherein the solid material fed into the enclosure is a thermoplastics resinous material suitable for marking road surfaces.
 13. Apparatus as claimed in claim 4, wherein the material is fed the the enclosure in powder form.
 14. Apparatus as claimed in claim 4, wherein the conveying path is a zig-zag path defined by baffles in the enclosure, the path having a generally constant cross-sectIonal area.
 15. Apparatus for spraying material, comprising: a. an endless, closed-loop, elongated enclosure defining a continuous conveying path, b. means for feeding solid material into said enclosure, c. means for conveying said material through the entire enclosure along said conveying path, d. means for heating said material to a predetermined temperature while it is being conveyed to produce a liquefied part of the material, and e. outlet means for discharging at least a portion of said liquefied part from the enclosure, f. said outlet means including at least one spray gun and means for recirculating liquefied material which has not been discharged from the spray gun directly back into said enclosure, g. said apparatus being adapted to be transportable on a vehicle.
 16. Apparatus as claimed in claim 15, wherein the enclosure includes at least one heating jacket disposed around the enclosure for heating the material being conveyed within said enclosure.
 17. An apparatus as claimed in claim 16, wherein there is a plurality of heating jackets disposed around different portions of said conveying half, and there is a means for heating each of the heating jackets at a different temperature with respect to each other.
 18. Apparatus as claimed in claim 15, wherein said feeding means includes means for controlling the amount of solid material fed into the enclosure in response to an amount of liquefied material being discharged from said enclosure. 